1. Field of the Invention
The present invention relates to a balancing plate for a motor. In particular, the present invention relates to a balancing plate having at least two induction edges, each induction edge having an arc length that mates with a length of one of plural poles of the annular permanent magnet on a rotor, thereby allowing stable rotation of the motor and allowing easy restarting of the motor by means of preventing the rotor from being locked by excessive magnetic attractive force between the respective induction edge and the permanent magnet.
2. Description of the Related Art
FIG. 1 of the drawings illustrates a motor and a conventional balancing plate therefore. FIG. 2 is a plan view of the motor and the balancing plate after assembly. As illustrated in FIGS. 1 and 2, the conventional motor 1 comprises a rotor 10, a stator 2, a balancing plate 30, and a circuit board 40 that are assembled along an axial direction to thereby form the motor. The balancing plate 30 includes an axial hole 31 and a plurality of induction edges 32 each having a predetermined arc length a. The induction edges 32 are preferably sector-like and diametrically, symmetrically arranged. The rotor 10 has a permanent magnet 11 that is radially spaced from the silicon steel plates 21 of the stator 20. The rotor 10 is driven by alternating magnetic fields generated by the silicon steel plates 21. The balancing plate 30 is located on the permanent magnet side of the rotor 10 such that the balancing plate 30 and the permanent magnet 11 of the rotor 10 always have an induction force therebetween regardless of the fact that the motor 1 is turning or stopped, thereby providing an appropriate inductive magnetic force to the rotor 10. In fact, the inductive magnetic force provided by the induction edges 32 of the balancing plate 30 is a downward, attractive balancing force, which is also a damping force in a way. Namely, the damping force will reduce the rotational efficiency. When the arc length a of the respective induction edge 32 of the balancing plate 30 is too long; namely, the arc length a of the respective induction edge 32 of the balancing plate 30 is greater than the length of the respective pole of the annular permanent magnet 11 of the rotor 10, an excessive inductive magnetic force is generated between the balancing plate 30 and the rotor 10, resulting a decrease in the rotational efficiency of the motor. Further, when the motor 1 is stopped, restarting of the motor 1 would not be easy in view of the excessive inductive magnetic force generated between the balancing plate 30 and the rotor 10. If the arc length a of the respective induction edge 32 of the balancing plate 30 is too short, the balancing force is insufficient for the rotor 10 such that the rotor 10 would xe2x80x9cwobblexe2x80x9d and xe2x80x9cfloatxe2x80x9d during rotation. Therefore, the arc length a of the respective induction edge 32 of the balancing plate 30 needs to be redesigned so as to provide the rotor 10 with sufficient balancing force and to allow easy restarting of the motor 1.
It is the primary object of the present invention to provide a balancing plate having at least two induction edges, each induction edge having an arc length that is equal to or less than a length of one of plural poles of the annular permanent magnet on a rotor. Thus, the arc length of the respective induction edge mates with the length of the respective pole of the annular permanent magnet, thereby avoiding generation of excessive inductive magnetic force and allowing easy restarting of the motor.
It is the secondary object of the present invention to provide a balancing plate having at least two induction edges, each induction edge having an arc length that is equal to or less than a length of one of plural poles of the annular permanent magnet on a rotor. Thus, the arc length of the respective induction edge mates with the length of the respective pole of the annular permanent magnet, thereby providing sufficient inductive magnetic force and allowing stable rotation of the motor.
A balancing plate in accordance with the present invention is to be assembled with a rotor, a stator, and a circuit board to form a motor. The balancing plate comprises an axial hole for engagement with a stator and at least two induction edges symmetrically arranged with respect to the axial hole. Each induction edge includes an arc length that is not greater than a length of one of plural poles of an annular permanent magnet of a rotor. When the motor rests, the induction edges of the balancing plate face at least two of the poles of the annular permanent magnet having the same polarity, forming a mating therebetween to thereby allow easy restarting of the motor.
Other objects, specific advantages, and novel features of the invention will become more apparent from the following detailed description and preferable embodiments when taken in conjunction with the accompanying drawings.